XML 和 java对象相互转换

比眉伴天荒 2021-06-24 14:00 569阅读 0赞

xml和Java对象的转换不需要任何的第三方包，JDK自带这个转换API，方便简洁。

下面使用的是JDK自带的类，没有引用任何第三方jar包。

Unmarshaller 类使客户端应用程序能够将 XML 数据转换为 Java 内容对象树。

备注：marshal(序列化、排列、整理)

Marshaller 类使客户端应用程序能够将 Java 内容树转换回 XML 数据。

实体类(这个是要被包含的实体类，不需要加注解)一:

package org.ywzn.po;
    
    public class User {
    
    	private String id;
    
    	private String name;
    
    	private String passwrod;
    
    	public User() {
    		super();
    	}
    
    	public User(String id, String name, String passwrod) {
    		super();
    		this.id = id;
    		this.name = name;
    		this.passwrod = passwrod;
    	}
    
    	public String getId() {
    		return id;
    	}
    
    	public void setId(String id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public String getPasswrod() {
    		return passwrod;
    	}
    
    	public void setPasswrod(String passwrod) {
    		this.passwrod = passwrod;
    	}
    
    	@Override
    	public String toString() {
    		return "User [id=" + id + ", name=" + name + ", passwrod=" + passwrod
    				+ "]";
    	}
    
    }

实体类二:

package org.ywzn.po;
    
    import javax.xml.bind.annotation.XmlRootElement;
    
    @XmlRootElement
    public class Room {
    
    	private String id;
    
    	private String address;
    
    	private User user;
    
    	public Room() {
    		super();
    	}
    
    	public Room(String id, String address, User user) {
    		super();
    		this.id = id;
    		this.address = address;
    		this.user = user;
    	}
    
    	public String getId() {
    		return id;
    	}
    
    	public void setId(String id) {
    		this.id = id;
    	}
    
    	public String getAddress() {
    		return address;
    	}
    
    	public void setAddress(String address) {
    		this.address = address;
    	}
    
    	public User getUser() {
    		return user;
    	}
    
    	public void setUser(User user) {
    		this.user = user;
    	}
    
    	@Override
    	public String toString() {
    		return "Room [id=" + id + ", address=" + address + ", user=" + user
    				+ "]";
    	}
    
    }

注意：

1、需要转换的model对象一定要添加@XmlRootElement注解，其里面的其他对象则不需要

2、需要转换的model对象一定要有不带参数的构造方法，包括该对象里面引用的对象。

测试Java对象转xml:

输出:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><room><address>桂林</address><id>1</id><user><id>1</id><name>夏小雪</name><passwrod>111</passwrod></user></room>

测试xml转Java对象:

package org.ywzn.main;
    
    import java.io.StringReader;
    
    import javax.xml.bind.JAXBContext;
    import javax.xml.bind.JAXBException;
    import javax.xml.bind.Unmarshaller;
    
    import org.ywzn.po.Room;
    
    public class App2 {
    
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		String xmlStr = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><room><address>厦门</address><id>1</id><user><id>1</id><name>易中天</name><passwrod>111</passwrod></user></room>";  
            try {  
                JAXBContext context = JAXBContext.newInstance(Room.class);  
                Unmarshaller unmarshaller = context.createUnmarshaller();  
                Room room = (Room)unmarshaller.unmarshal(new StringReader(xmlStr));  
                System.out.println(room);
            } catch (JAXBException e) {  
                e.printStackTrace();  
            }  
    	}
    
    }

输出:

Room [id=1, address=厦门, user=User [id=1, name=易中天, passwrod=111]]

测试编码与是否省略xml头:

package org.ywzn.main;
    
    import javax.xml.bind.JAXBContext;
    import javax.xml.bind.JAXBException;
    import javax.xml.bind.Marshaller;
    
    import org.ywzn.po.Room;
    import org.ywzn.po.User;
    
    public class Java2XMLSetEncode {
    
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    
    		User user = new User("1", "夏小雪", "111");
    		Room room = new Room("1", "桂林", user);
    		try {
    			JAXBContext context = JAXBContext.newInstance(Room.class);
    			Marshaller createMarshaller = context.createMarshaller();
    			createMarshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");// 编码格式
    			createMarshaller
    					.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);// 是否格式化生成的xml串
    			createMarshaller.setProperty(Marshaller.JAXB_FRAGMENT, false);// 是否省略xml头信息（<?xml
    
    			createMarshaller.marshal(room, System.out);
    			
    			
    		} catch (JAXBException e) {
    			e.printStackTrace();
    		}
    	}
    
    }

输出结果:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
    <room>
        <address>桂林</address>
        <id>1</id>
        <user>
            <id>1</id>
            <name>夏小雪</name>
            <passwrod>111</passwrod>
        </user>
    </room>

JAXB（Java Architecture for XML Binding) 是一个业界的标准，是一项可以根据XML Schema产生Java类的技术。该过程中，JAXB也提供了将XML实例文档反向生成Java对象树的方法，并能将Java对象树的内容重新写到XML实例文档。从另一方面来讲，JAXB提供了快速而简便的方法将XML模式绑定到Java表示，从而使得Java开发者在Java应用程序中能方便地结合XML数据和处理函数。

JAXBContext 类提供到 JAXB API 的客户端入口点。它提供了管理实现 JAXB 绑定框架操作所需的 XML/Java 绑定信息的抽象，这些操作包括：解组、编组和验证。